1. Field of the Invention
This invention belongs to the field of agricultural chemistry and provides to the art new herbicides and herbicidal methods. Herbicides are now commonly used in the culture of virtually every crop and ornamental plant. It has been proved again and again that the proper use of herbicides for the elimination of weeds is necessary to maximize production. Appropriately chosen herbicides free the crop from the competition of weeds for the available water, nutrients and sunlight. Herbicides, when properly used, produce benefits in absolute yield and in economic profit which far outweigh the expense of the chemicals.
2. Description of the Prior Art
The 1,3,4-thiadiazol-2-ylureas as a group have been the subject of research in agricultural chemistry, and have been used as herbicides in the past. For example, British Pat. Specification No. 1,290,223, published Sept. 20, 1972, discloses thiadiazolylureas bearing a variety of substituents in the 5-position of the thiadiazole ring, none of which substituents contain the sulfamoyl moiety.
Another prior art reference is British Pat. Specification No. 1,230,432, published May 5, 1971, which teaches 1,3,4-thiadiazol-2-ylureas having alkyl, alkenyl, cycloalkyl, and alkylthio substituents attached at the 5-position of the thiadiazole ring.
British Pat. Specification No. 1,254,468, published Nov. 24, 1971, discloses 5-perfluoroalkylthiadiazolylureas.
Cebalo, South African Patent No. 69/1559, teaches 1,3,4-thiadiazolylureas bearing acyclic groups in the 5-position.
In addition, U.S. Pat. No. 3,726,892 (Apr. 10, 1973), teaches a number of 5-sulfamoyl-1,3,4-thiadiazol-2-ylureas alleged to have particular use as herbicides. This patent discloses a 5-morpholinosulfamoyl compound without specifically illustrating any activity for it.
Additional 5-sulfamoyl compounds, bearing various hydrocarbyl substituents on the sulfamoyl nitrogen, are disclosed by British Pat. Specification No. 1,340,267, published Dec. 12, 1973, as well as by Belgian Pat. No. 767,177.